There is currently a significant amount of interest in the next generation sequencing technologies that are being commercialized. Presently the commercial offerings range from systems that claim to achieve from 40 to 100MB of sequence information in a single run, up to about 1 to almost 2 GB of assembled sequences in a single run.
A feature of several of the recent commercial offerings is a solid phase single molecule clonal amplification procedure based either on bead emulsion PCR, or on bridge PCR. This clonal amplification enables a single DNA molecule to be amplified on solid phase, which physically separates one molecule from another. After amplification, these distinct clusters of DNA are then subject to repeated cycles of ligation or reversible single base chain terminated extension. During these reactions, separate labeling with 4 florophores or haptens, one for each of the 4 DNA bases, allows for the identification of the incorporated base at any given position. Repeated cycles generate short fragments of DNA sequence which can then be assembled into a larger continuous length of finished sequence. The DNA sequencing approach is therefore random and currently does not specifically sample any targeted regions of interest.